(1) Field of the Invention
The invention relates to an axially damping hydraulic mount. The invention relates to elastomer mounts with hydraulic damping of the type used for example in automotive engineering as engine or equipment mounts for damping the vibrations transmitted from the internal combustion engine to the body and for acoustic decoupling.
(2) Description of Related Art
Engine mounts and equipment mounts, respectively, are constructed essentially of a metallic mount core by which the mount is typically also attached on the engine or the equipment, of a mostly two-part outer jacket and a frustoconical elastomer support spring arranged between the mount core and an upper part of the outer jacket. Depending on the configuration, the aforementioned parts are further received by a housing with which the parts of the outer jacket of the mount are frequently held together. If the mount is provided with hydraulic damping, then the aforementioned elastomer support spring surrounds a working chamber receiving a fluid damping means. This working chamber is separated from an equalizing chamber by a separating element, namely a membrane, a so-called nozzle plate and the like, which extends transversely to the mount axis. The equalizing chamber is surrounded by an elastomer bellow which is typically protected by a lower part of the outer jacket. In the region of the separating element which separates the working chamber and the equalizing chamber, the working chamber and the equalizing chamber are connected with each other by a duct, which allows damping means to pass between the working chamber and the equalizing chamber. If vibrations act axially on the mount, the damping means can then move out of the working chamber into the equalizing chamber during deflection and move back from the equalizing chamber into the working chamber during rebound. The back and forth oscillation of the fluidic damping means provides additional damping for axially acting vibrations.
In the design of the engine mounts, it is particular difficulty to design the engine mounts so as to provide effective acoustic coupling between the engine and the body, which would prevent noise generated by high-frequency vibrations of the engine to be transferred to the body. In particular, the large number of parts of which the mount is constructed produces problematic partial resonances at different locations of the mount, which may also mutually influence each other at least partially. In particular at higher frequencies, such partial resonances cause an undesired enhancement of the dynamic spring rate of the mount and hence lead to a deterioration of the acoustic decoupling. The quality of the noise insulation of the engine mount is hereby frequency-dependent. However, it is quite difficult to identify the individual partial resonances and the respective locations where they occur and to reduce occurrences of these resonances while maintaining all other properties required from the mount, such as damping, idling decoupling and spring rate ratios in the different spatial directions.